Re: [PATCH v5 4/9] x86/traps: Enable all exception handler callbacks early

[Andy Lutomirski]

On Sun, Apr 3, 2016 at 6:51 AM, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Sun, Apr 3, 2016 at 3:07 AM, Borislav Petkov <bp@xxxxxxxxx> wrote:
>>
>> I'm wondering whether making it try to EFAULT correctly is the right
>> thing to do... We're certainly more conservative if we panic and not
>> allow some silently failed attempt at recovery which looks successful,
>> to continue.
>
> No, please don't fail at early boot.
>
> Early boot is just about the *worst* situation to try to debug odd
> failures, exactly since things like printk may not be reliable, and
> things won't get logged etc.
>
> So particularly during early boot we should try as hard as possible
> not to crash - even if it means not being able to log about a problem.
> At least that way you have a hopefully working machine and can *maybe*
> debug things.
>

In this regard, at least, my patch is the right approach.  Calling the
handler, whatever it is, is less likely to panic than refusing to call
it.

--Andy